This invention relates to a system controlling apparatus and relates particularly, but not exclusively, to such for use in railway crossing signalling installations.
In its broadest aspect the invention has application to controlling apparatus, dependent on articles as they pass a series of adjacent sensors. Such might be where articles are moving past sensors on a conveyor belt and wherein operations are required to be performed either on the articles or at stations which receive the articles or where certain steps have to be taken as the articles pass. The articles, as they pass the sensors, cause generation of information concerning the passing of the articles such as presence of the article, number of articles passing and their speed of passing.
When applied to railway crossing signalling installations the sensors detect information as to the passing of train wheels at selected locations. The sensors detect information such as the presence of a train wheel at a sensor, the number of train wheels passing, the direction of passing and the velocity of passing. Such information is compared with similar information obtained from other sensors in the crossing installation to see if the same number of wheels are passing those sensors, whether the direction of movement has changed and whether the velocity has changed. All this information is fed to a controller which acts on the information and decides whether actions should be taken downstream having regard to the information detected regarding the passing of the train wheels. Such information may be that a warning signal at the crossing should be activated and/or boom gates lowered.